(This question deals principally with the physics and metaphysics of 3/3.5E)

It costs 250gp at 5th level to turn ten ordinary impoverished humans into mindless fleshless murder machines that can sprint basically forever and can't be reasoned or bargained with and absolutely will not stop until you are dead.

It's not like folks are expecting the departed to be restored to their earthly bodies after Armageddon. Any (honest) Cleric will tell you: the afterlife is huger and stranger and crazier and cooler than you can imagine. Once passed, you can graduate through the hierarchies of a limitless planar paradise and become king of infinite space.

It makes sense that if your household can afford Resurrection you might hang onto really exceptional specimens - those once in a lifetime souls who stop the Lich and claim the dragon's hoard. But everyone else is basically a necromancer's ammunition.

The real question is why anyone living is still tilling the fields or digging for gold or fighting the wars, and why benevolent necromancers haven't made the world a paradise built on the tireless, guilt-free labour of the unliving.

The simple answer to that, dear Steerpike, is that zeds and skellywags are "always neutral evil" (whatever that means) and Animate Dead is always [Evil] (whatever that means). You can't use their powers for good. It's the rules.

I could see the "always evil" thing being a more plausible obstacle to necrobotics if you assume that the mindless undead are not just automatons to be commanded to do whatever but rather walking embodiments of pure death itself seething with necrotic energy. D&D kind of touches on this, where it specifies that mindless undead that aren't under anyone's command will basically flip out and attack whoever. So maybe it's just too risky to employ undead labor, because there's always a fairly good chance that whatever control magic you have will fail and you'll suddenly have a murderous horde on your hands.

Which, of course, could make a great adventure scenario in this setting...

I'm just brainstorming at work but my current spin on this concept is that the undead are scary and alien and apparently "mindless"' largely because they're unencumbered from all those endocrine urges. Laboring endlessly out of pure love for the commune and tirelessly slaughtering anything in their path are two sides of the same coin.

sparkletwist

So maybe it's just too risky to employ undead labor, because there's always a fairly good chance that whatever control magic you have will fail and you'll suddenly have a murderous horde on your hands.

This is a super cool idea.

Also it's basically a Marxist account of revolution: "So maybe it's just too risky to employ undeadproletarian labor, because there's always a fairly good chance that whatever control magicideological mechanisms of oppression you have will fail and you'll suddenly have a murderous horde on your hands (demanding the means of production).

Steerpike

The real question is why anyone living is still tilling the fields or digging for gold or fighting the wars, and why benevolent necromancers haven't made the world a paradise built on the tireless, guilt-free labour of the unliving.

Guilt-free, sir?

Why do you think those uncontrolled skeletons attack the living? They're "mindless," after all. They don't have a malevolent will. But they are animated by negative energy which, if not exactly sapient, is clearly a feeling thing. Think about it: you're a ball of negative energy ripped from your cozy Plane of Negative Energy and thrust into a word full of life, which for you is like goddamn antimatter on fire. You've been trapped in this place inside a prison of flesh and bone and, just to top it all off, imbued with just enough awareness and comprehension to follow instructions.

A skeleton doesn't "think," exactly, but insofar as it does, this is what it is thinking all the time: "AAAAHHH IT BURNS AAAAH AAAAAAAAAAAAH"

Creating undead isn't evil because of what it does to human bodies. Nobody cares about bodies, they're dead. It's negative energy torture-slavery. And since the energy is sub-sentient it's like enslaving an animal. Basically, raising a skeleton for farming is the moral equivalent of creating an immortal puppy and torturing it for eternity so you don't have to get your hands dirty.

Pareidollhouse

BASTARDS. UN-LIVES MATTER.

That's right you awful CIS-Natural Normies. Don't make other beings conform to your oppressive standards of "life"! Did that negative energy choose to be negative energy?

But in all seriousness, you're not wrong. Another question I've always had from a narrative structure is "Why don't dragons rule the world?" The only published setting I've seen that dealt with this question was Eberron. Speaking of Eberron, Karrnath had an interesting twist on this, where if you died, you would have your corpse reanimated into zombie soldiers.

My gaming group's answer has long been that metallic dragons do rule the world.

Since all true dragons "can metabolize even inorganic material", and metallics seem to be vegetarian or piscetarian (when they aren't eating pearls of gemstones or morning dew), when it says that "Red dragons are meat eaters by preference, and their favorite food is a human or elven youth," it means that Reds (the smartest chromatics) really are CONGENITALLY TERRIBLE PEOPLE; they can't help themselves, always self-sabotaging, pissing off everybody around them with their bad decisions, generally being assholes.

By contrast: "A gold dragon often assumes human or animal guise"; "Silver dragons seem to prefer human form to their own, and they often have mortal companions, even forming deep friendships"; and "Bronze dragons are inquisitive and enjoy polymorphing into small, friendly animals to observe adventurers. They are fascinated by warfare, eagerly joining an army for a just cause—and good pay". A metallic dragon is a total mensch, prizing humanoids' self-determination so highly she doesn't solve their problems for them, even though she can, and even when she does she makes it look like a humanoid did it, so that the lesser races don't become dependent. It's also worth noting that Golds and Silvers are the smartest of all core dragons, while bronze dragons are as smart as Reds. The bad dragons don't realise it, but everybody's laughing about them behind their backs.

EDIT: also, wandering far from DnD canon as I understand it: dragons have huge hoards not merely because they like the look of glittering gold, trinkets and baubles, but because they understand material value and how to leverage it. Their hoards are both the shiny beds they sleep on, and the secrets they keep concealed beneath them (or keep locked away in their ancient memories). Bronze, Gold and Silver dragons are, more than anything else, masters of secrets, and they make better use of such leverage than other dragons because they are smarter AND more disciplined.